Abstract : The report gives the results of a study of genetic criteria of the following group A2 virus strains: Krasnodar-101/59, Leningrad-1764/59, England-12/64, Moscow-21/65, Leningrad-29/65 and Leningrad-151/65. Tests were made on animals to study sensitivity to inhibitors, infection and hemagglutinating activity, thermostability, ability to elute from erythrocytes and to multiply at various incubation temperatures and antigen activity. Methods of study have been described previously (Kolchurina, 1963).